Morning-after pill ineffective for heavier women, drugmaker says

A commonly used morning-after pill doesn’t work for women weighing more than 176 pounds, its European maker says.

Plan B is found on drugstore shelves across Canada. The emergency contraceptive may lose effectiveness for women who weigh more than 165 pounds and doesn’t work at all for women over 176 pounds, the company that makes the drug in Europe says.

The morning-after pill may not prevent unwanted pregnancies in heavier women, says the European manufacturer of the drug.

In Canada the pill known as Plan B is marketed by Montreal-based Paladin Labs Inc. and contains 1.5 milligrams of the synthetic hormone levonorgestrel, the same active ingredient as the European product sold under the brand name NorLevo.

French pharmaceutical company HRA Pharma announced this week it would change the packaging labels on its emergency contraception to reflect its finding that NorLevo begins to lose effectiveness in women who weigh more than 165 pounds or have a Body Mass Index (BMI) of 25 and doesn’t work at all for women over 176 pounds or have a BMI of 30.

In Europe the new label will read: “In clinical trials, contraceptive efficacy was reduced in women weighing 75 kilograms or more and levonorgestrel was not effective in women who weighed more than 80 kilograms.”

Montreal’s Paladin Labs, which sells Plan B in drugstores across the country without a prescription, is waiting for direction from both Health Canada and Teva Pharmaceuticals, the American manufacturer of the drug.

“It is a different product in Europe, it’s a different company. Same ingredient, different product,” said Patrice Larose, vice-president of scientific affairs for Paladin Labs.

“Teva has not commented yet in the U.S. or Canada,” Larose said, adding he was “waiting to see their position.”

“It does not apply to our product at this point in time. It will be Health Canada’s decision to see if it applies or not.”

Although the Food and Drug Administration said Tuesday it was reviewing the available scientific information on NorLevo, its U.S. drugmaker said it could not comment on the efficacy of the pill.

Both pills have the same active ingredient and directions for use, 1.5 milligrams of levonorgestrel to be taken immediately after unprotected sex, although the European version is not approved in the U.S., said Denise Bradley, vice-president of corporate communications for Teva Pharmaceuticals in the Americas.

But whether North American women are affected remains unclear. The Society for Obstetricians and Gynaecologists of Canada, which gives direction to health care agencies including Planned Parenthood, said it would have to review the research before responding.

Health Canada said in a statement Tuesday the department was “assessing the available data on the effectiveness of this product, and will take appropriate action if required, such as working with the manufacturer to update the product labelling and notifying healthcare professionals and consumers of this change.”

Spokeswoman Leslie Meerburg said there was no timeline for the assessment.

The study in question was published in the journal Contraception in 2011 but is only making waves now that the French manufacturer is changing its label, said Diana Blithe, an author of the study and program director for contraceptive research at the U.S. National Institute of Child Health and Human Development in Bethesda, MA.

The effect of weight on the pill’s efficacy “fell out” of a meta-analysis of clinical trials comparing two HRA Pharma products: NorLevo and another emergency contraceptive pill known as Ella, made of the compound known as ulipristal acetate, which is not approved in Canada.

It’s long been suspected that oral contraception is less effective in obese or overweight women, Blithe said.

Because researchers weren’t recruiting for overweight women in the study, a relatively small number of women who had a Body Mass Index (BMI) over 25 and who were at risk for pregnancy based on their menstrual cycle were included in the data, Blithe said.

Of 3,445 women included in the analysis, only 744 were considered overweight and 469 were obese. Among obese women, the incidence of pregnancy after taking emergency contraception was 5.8 per cent, which is slightly higher than the overall pregnancy rate of unprotected sex.

Wendy Norman, a physician and professor at the University of B.C., and leader of the national Contraception Access Research Team, cautioned against reading too much into the recent study.

The raw data used were part of a clinical trial comparing two HRA Pharma products and not made publicly available.

Plan B remains a good “last ditch” course of action, but accessing a doctor for the insertion of a copper intrauterine device is the best way — more than 20 times as effective as Plan B — to avoid an unplanned pregnancy, she said.

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